1. Field of the Invention
The present invention relates to an agitator, an image forming apparatus having the same, and a method for agitating compounds.
2. Description of the Related Art
Generally, image forming apparatuses such as laser printers, copy machines and multi-function apparatuses are divided into two groups: a dry-type image forming apparatus and a wet-type image forming apparatus. The dry-type image forming apparatus uses a powdery toner as a developer. The wet-type image forming apparatus uses a liquid carrier, such as norpar, mixed with the toner. In both types of image forming apparatuses, the toner is supplied to an image carrier, such as a photoconductive drum, where an electrostatic latent image is formed, thereby developing an image. The developed image is printed onto a printing medium passed through a transfer medium rotating in contact with the photoconductive drum. Presently, the wet-type developing method is widely used.
A general wet-type image forming apparatus supplies a liquid developer of a certain density to a developing device and develops an electrostatic latent image formed on the image carrier such as the photoconductive drum.
The developing device may comprise, for example, a developer reservoir mounted in the vicinity of the image carrier, a developing roller mounted in the developer reservoir to transfer the developer to the image carrier, a manifold for jetting and transferring the developer to the developing roller, and a squeeze roller for removing excessive developer of the developing roller to restrict thickness of the developer.
The developer supplied to the manifold is mixed with enough toner to maintain a predetermined density. For this, a dedicated working solution tank is provided to control the developer density by mixing the liquid carrier and the powder toner by a predetermined mixture ratio. However, the dedicated working solution tank complicates the whole structure.
Therefore, a new method has been developed, in which the toner and the carrier are mixed at a predetermined density during the manufacturing process and is supplied mixed and stored in a developer cartridge. This method does not necessitate a dedicated density controller. The user only needs to replace the developer cartridge, which is more convenient.
However, in such a pre-mixed developer, the powdery toner may precipitate and clot if the image forming apparatus is left unused for a long time. Accordingly, an agitator is required to agitate the developer.
When the carrier and the toner are evenly mixed, the agitator can be driven with minor driving force, however, when the developer has precipitated and clotted for a long time, a greater amount of driving force is required for agitating the toner sludge.
Accordingly, there is a need for an agitator that requires a minimal driving force for agitating a toner sludge or developer using a single driving source.